"The City of Rocks National Reserve, jointly administered by the National Park Service, Idaho Department of Parks and Recreation, and local authorities, received the national attention to designate it as a Reserve largely because of its position on historic emigrant routes, including the California Trail. Emigrants passing through the stunningly scenic landscape of giant rock spires and pinnacles dubbed the area the "Silent City of Rocks" and signed their names on many pinnacles. As a result, geology has a key place in the founding of this Reserve, for the geologic landforms led to the cultural resources. Geology also is a key contributor to land-resource management decisions, because the susceptibility of surface materials to erosion, deposition, and destructive processes such as landsliding require geological study. The surface materials also partly control vegetation distribution and habitats, and may influence invasion of exotic species."
http://pubs.usgs.gov/of/1999/of99-386/bedford.html